1. Field of the Invention
The present invention relates to defoaming methods and compositions, and more particularly, to such methods and compositions for preventing the formation of foam and the like or breaking foam in liquid fluids.
2. Description of the Prior Art
Defoaming compositions have long been used in the oil and gas industry and other industries to prevent the formation of a foam or the entrainment of a gas in a liquid fluid or to destroy a previously formed foam. The defoaming compositions are commonly utilized, for example, as components in well treating fluids to prevent the formation of foam or the entrainment of a gas in a liquid fluid during the preparation and or pumping of the fluid. Also, defoaming compositions have been utilized heretofore for breaking previously formed foamed liquid fluids. For example, when a stable foamed well treating fluid must be disposed of on the surface, a defoaming composition is added to the fluid to destroy the foam whereby the liquid components of the treating fluid can be readily disposed of.
A variety of defoaming compositions have been utilized heretofore. Examples of such defoaming compositions utilized in well treating fluids include tributyl phosphate and acetylenic diol, which are environmentally toxic. Other prior art defoaming agents, which have been utilized include propylene glycol and a mixture of propylene glycol with a copolymer of ethylene oxide and propylene oxide monomers. While these defoamers function adequately to prevent the formation of foam in well treating fluids when they are prepared and pumped, they do not function adequately for defoaming previously formed foamed well treating fluids, and particularly previously formed foamed well cement compositions. Thus, there is a continuing need for improved environmentally safe defoaming compositions for use in various fluids including well treating fluids.
The present invention provides improved non-toxic environmentally benign defoaming methods and compositions which meet the needs described above and overcome the deficiencies of the prior art. A method of this invention for preventing the formation of foam or the entrainment of a gas in a liquid fluid is comprised of combining a defoaming composition with the fluid, the defoaming composition being comprised of a mixture of glycerol tristearate and one or more aliphatic hydrocarbons selected from the group consisting of olefins having one or more internal double bonds and having 14 to 18 carbon atoms and a C10 dimer of the formula 
Another method of this invention for defoaming a foamed liquid fluid comprises combining a defoaming composition with the fluid, the defoaming composition being as described above.
A non-toxic environmentally benign defoaming composition for preventing the formation of foam or the entrainment of a gas in a liquid fluid or for defoaming a foamed liquid fluid is comprised of a mixture of glycerol tristearate and one or more aliphatic hydrocarbons selected from the group consisting of olefins having one or more internal double bonds and having 14 to 18 carbon atoms and a C10 dimer of the formula 
It is, therefore, a principal object of the present invention to provide improved defoaming methods and compositions.
Other and further objects features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
As mentioned above, defoaming compositions are commonly utilized in a variety of liquid fluids to prevent the fluids from forming foam with air or entraining air when they are agitated, mixed or the like in the presence of air. In the treatment of wells with well treating fluids, the liquid fluids are commonly mixed or blended in the presence of air on the surface and then pumped into the well bore. If the well treating fluids are inadvertently foamed while being mixed and pumped, adverse results can take place. For example, in completing and stimulating a well, unfoamed treating fluids are often utilized which if foamed would not accomplish their intended purposes or would produce less than desirable results. For example, well cement compositions used for cementing pipe in well bores are generally designed to have a specific density. If during mixing or pumping the well cement composition is foamed with air or otherwise entrains air, the density of the resulting cement composition can be considerably lower than the desired or required density. Also, foam or entrained air interferes with the operation of positive displacement pumps used to pump well treating fluids.
While well treating fluids are often formed into stable foams on the surface in order to reduce the density of the fluids or for other reasons. When such stable foams must be disposed of on the surface, it is generally necessary to break the foams in order to efficiently dispose of the liquid components. While defoaming compositions have been developed and used successfully heretofore, such defoaming compositions generally have either been environmentally toxic or have produced less than desirable results when utilized to break stable foams. By the present invention, improved methods and defoaming compositions are provided which are non-toxic and environmentally benign and also produce equal or better defoaming results than the heretofore utilized defoaming methods and compositions.
The improved defoaming compositions of this invention are basically comprised of a mixture of glycerol tristearate and one or more aliphatic hydrocarbons selected from the group consisting of olefins having one or more internal double bonds and having 14 to 18 carbon atoms and a C10 dimer of the formula 
The one or more aliphatic hydrocarbons are preferably comprised of a mixture of C16 to C18 olefins having internal double bonds or a mixture of C14 to C16 olefins having internal double bonds or a dimer having the formula set forth above. Generally, the weight ratio of the glycerol tristearate to the one or more aliphatic hydrocarbons utilized is in the range of from about 5:95 to about 10:90. More preferably, the weight ratio of the glycerol tristearate to the one or more aliphatic hydrocarbons is about 8.34:91.66.
A preferred non-toxic and environmentally safe defoaming composition of this invention is comprised of a mixture of glycerol tristearate and a C10 dimer of the formula 
the weight ratio of the glycerol tristearate to the dimer being about 8.34:91.66.
The methods of the present invention of preventing the formation of foam or the entrainment of a gas in a liquid fluid during the preparation or pumping of the liquid fluid comprises combining a defoaming composition with the liquid fluid, the defoaming composition being comprised of a mixture of glycerol tristearate and one or more aliphatic hydrocarbons selected from the group consisting of olefins having one or more internal double bonds and having 14 to 18 carbon atoms and a C10 dimer of the formula 
While the liquid fluid can be any liquid fluid in which it is desirable to prevent foaming or air entrainment, the defoaming compositions of this invention are useful in well treating fluids and particularly well cement compositions for preventing foaming or air entrainment while mixing or pumping such fluids. The defoaming composition is generally combined with the liquid fluid in an amount in the range of from about 0.1% to about 0.5% by weight of the fluid. As mentioned above, the defoaming composition can also be utilized for defoaming a previously prepared stable foamed liquid fluid so that the liquid components of the foamed fluid can be readily and safely disposed of. When used as a defoamer, the defoaming composition is generally combined with the foamed liquid fluid in an amount in the range of from about 0.1% to about 1.0% by weight of the liquid fluid in the foamed liquid fluid.
A preferred method of the present invention for preventing the formation of foam or the entrainment of a gas in a liquid fluid or for defoaming a previously foamed liquid fluid is comprised of combining a defoaming composition with the fluid, the defoaming composition being comprised of a mixture of glycerol tristearate and one or more aliphatic hydrocarbons selected from the group consisting of a mixture of C16 to C18 olefins having internal double bonds, a mixture of C14 to C16 olefins having internal double bonds or a C10 dimer having the formula 
the weight ratio of the glycerol tristearate to the one or more aliphatic hydrocarbons being in the range of from about 5:95 to about 10:90.
As will now be understood, the defoaming composition of this invention can be utilized in a variety of different fluids and are particularly well suited for use in well treating fluids. Examples of well treating fluids in which the defoaming compositions can be utilized to prevent the formation of foam or the entrainment of air are aqueous gelled fluids and cement compositions. An example of a previously prepared foamed well treating fluid which can be efficiently defoamed using the defoaming composition of this invention is a stable cement composition foamed with air or nitrogen. Excess previously prepared stable foamed well cement compositions are often pumped into pits on the surface and must be disposed of. By combining a defoaming composition of this invention with the foamed cement compositions, e.g., by spraying the defoaming composition thereon, the foamed cement compositions rapidly and completely break whereby their liquid components can be readily disposed.